ANGLES IN TRIANGLES
Math 8
Triangles –
Classification by Angle size
Acute Triangle
all three angles
are acute ( < 90º)
Right Triangle
one angle is 90º
Obtuse Triangle
one angle is
obtuse ( > 90º)
Triangles –
Classification by Side length
Scalene Triangle
all three sides are
different lengths
Isosceles Triangle
two sides are
congruent lengths
Equilateral Triangle
all three sides are
congruent lengths
Draw a triangle with one obtuse angle and no congruent sides.
Classify the triangle
Obtuse
Scalene
Draw a triangle with one right angle and two congruent sides.
Classify the triangle
Right
Isosceles
Classify each triangle shown by both angles and side length
Right
Scalene
Obtuse
Isosceles
Interior Angles of a Triangle
sum to 180°
straight line = 180°
Find the missing angle measurement
When the problem asks for the
Measure of the angle, you must
include the degree symbol º
Find the missing angle measurement
In , if , and what is ?
In , if , and what is ?
Find the value of x in each triangle
When the problem asks to solve for x you don’t include the degree symbol
Find the value of x in each triangle
Find the value of x in each triangle
Find the value of x in each triangle
(3x - 20)°
35°
Find the measure of the angles in if the ratio of their measures is 2:3:5
B
C
A
Find the measure of the angles in if the ratio of their measures is 1:5:6
X
Z
Y
Exterior Angles of a Triangle
-the Exterior Angle of a Triangle formed by extending one side is equal to the sum of the remote interior angles
interior of a triangle
straight line
Find the value of x in each triangle
Find the value of x in each triangle
Suppose
, what are the measures of the other numbered angles?